Laminate of foam and stitch bonded fabric

ABSTRACT

A WARP KNITTED FABRIC COMPRISING LOOSE FILLING THREADS HELD TOGETHER BY CHAIN STITCHES OF SEWING THREAD WHICH GATHER THE FILLING THREADS INTO CLUSTERS SEPARATED BY SPACES WHERE THE STITCHES PASS THROUGH THE FABRIC. THE FABRIC IS LAMINATED WITH A FOAMED POLYMERIC MATERIAL WHICH IS FLUID OR BECOMES FLUID DURING THE PROCESS SO THAT IT CAN FLOW INTO THE SPACES BETWEEN CLUSTERS OF FILLING THREADS AND INTERLOCK WITH THEM AND THE SEWING THREAD. AFTER FLOWING INTO POSITION WHILE FLUID THE FOAM IS GELLED AND, IF NECESSARY, CURED TO TAKE ON ITS PERMANENT CONFIGURATION.

Marlh 2, 1.971 R. L. JoNEs ETAL LAMINTE- OF FOAM AND STITCH BONDEDFABRIC .Filed N ov. 9, 1967 Patented Mar. 2, 1971 3,567,565 LAMINATE OFFOAM AND STITCH BONDED FABRIC Robert L. Jones, Greensboro, N.C., andRobert E.

Provost, Stamford, Conn., assignors to Burlington Industries, Inc.,Greensboro, N.C.

Filed Nov. 9, 1967, Ser. No. 681,703 Int. Cl. B32b 7/04 U.S. Cl. 161-506 Claims ABSTRACT OF THE DISCLOSURE A warp knitted fabric comprisingloose filling threads held together by chain stitches of sewing threadwhich gather the filling threads into clusters separated by spaces wherethe stitches pass through the fabric. The fabric is laminated with afoamed polymeric material which is fiuid or becomes fiuid during theprocess so that it can flow into the spaces between clusters of fillingthreads and interlock with them and the sewing thread. After flowinginto position while fluid the foam is gelled and, if necessary, cured totake on its permanent configuration.

DISCLOSURE The present invention relates to a fabric and moreparticularly to a warp knitted type fabric comprising chain stitchesholding together an array of loose filling threads transverse to thestitching, and to a method of making the fabric. In accordance with thisinvention, considerable increase in strength and dimensional stabilityis achieved by means of a foamed polymeric material laminated to oneside of the fabric and partially filling certain spaces between theloose filling thread.

Fabrics of the type mentioned above may be made on the type of apparatusdescribed in Mauersberger U.S. Pat. 3,030,786. In that apparatus, theloose filling threads are provided from continuous threads which arewound back and forth across a kind of tenter frame by a carriage, andaround heddle hooks on moving conveyor belts at either side of theframe. The conveyors are moving while the carriage traverses the spacebetween them, so that the filling threads are made more or le'ss obliqueto the machine direction and in two sets which are oblique to eachother. That is, after a set of parallel threads are caught on the hooksof one of the conveyors, it moves directly across to the other conveyor.While the carriage moves across, the conveyors are movingperpendicularly to the carriage and, by the time the carriage reachesthe other conveyor, it has moved a short distance. Therefore the heddlehooks on which the threads are caught on the second conveyor are notdirectly opposite the hooks used on the first conveyor, and the threadsare oblique to the machine direction. When the carriage returns to thefirst conveyor, an opposite effect is observed, and the threads laiddown are oblique to the machine direction and to the threads laid downin the previous traverse.

The conveyors move the filling threads to a sewing head Where a set ofneedles forms several lines of chain Stitches which bind the fillingthreads together. In some cases, the sewing thread supplied to theneedles is supplied alternately to adjacent needles and is sewedalternately into adjacent stitches. This causes a kind of interlockingeffect between adjacent lines of stitches which tends to reduce thelikelihood of ripping a chain of stitches if one loop is damaged. Theinterlocking stitch has the further advantage of permitting use of loosewarp threads which are simply laid on one side of the loose fillingthreads, but are not woven. The warp threads are held against thefilling threads by the sewing thread as it zig-zags back and forthbetween adjacent rows of stitches.

An important characteristic of the fabric produced is the arrangement ofthe filling threads after sewing. In many fabrics, the stitches may be,for example, 2-3 mm. apart. Between stitches, several filling threadsare clustered together relatively tightly, while at points wherestitches pierce the fabric, the filling yarn is pushed away. Thus thefabric has the appearance of spaced clusters of relatively parallelyarns separated by spaces at points where the sewing yarn pierces thefabric. There is a tendency for some of the filling yarns to cross thisspace, connecting adjacent filling yarn clusters, but generally speakingthe fabric appears to consist of spaced parallel 4filling yarn clusters.In some cases, the above-mentioned spaces are deliberately accentuatedby omitting filling yarn between some stitches. In these areas, thefabric has the form of warp knit goods.

'Fabrics of this type have significant cost advantages. Estimates haveindicated that one sewing machine can produce 20-40 times as much fabricas a loom. Relatively inexpensive material may be used as the -fillingyarn, further reducing costs.

The present invention is concerned with improving these fabrics byreinforcing them with a foamed polymer which adds relatively littleweight or stiffness to the fabric but increases its bulk and opacity,and provides an ornamental appearance. More specifically, the fabricdescribed above is laminated with a vpolymeric material which is eitherfoamed or is capable of being foamed. The polymeric material is eitherapplied as a fiuid or is applied as a material capable of becoming afluid during processing, so that it can penetrate partially the spacesbetween clusters of warp yarns. The fluid material is caused topenetrate partially those spaces and is gelled and, if necessary, cured,to form a layer of foamed polymer on one side of the fabric andinterlocked between the aforesaid clusters. The foam surrounds thesewing thread on one side of the fabric and portions of the sewingthread extending through the fabric at the stitches, and it also anchorswarp yarn,if any, between it and the filling yarn. Normally, warp yarn,if any, is on the same side of the fabric as the foam, unless it isbeing used for ornamental purposes.

If the polymer is colored or contains a coloring material which isdifferent from the yarn, it provides an ornamental effect of dots orlines of background showing through the fabric.

Substantially any yarn can be used for the filling and/ or sewingthread. These include natural fibers such as cotton,

wool, sisal, jute, flax and silk and synthetic fibers such 4 asregenerated cellulose (rayon), cellulose esters, e.g. cellulose acetate,cellulose acetate/butyrate and cellulose triacetate, acrylics, e.g.polyacrylonitrile, modacrylics, acrylonitrile-vinyl chloride copolymers,polyamides, e.g. polyhexamethylene adipamide (Nylon 66), polycaproamide(Nylon 6) and polyandecanoamide (Nylon 11), polyolefin, e.g.polyethylene and polypropylene, polyester, e.g. polyethyleneterephthalate, rubber and synthetic rubber, saran, glass, etc. Sewingyarn sizes ordinarily are about 40 to 200 denier and filling yarns from3,000 yds/lb. to about 20,000 yds/lb. When warp yarns are used, they maybe, e.g. from about 1,000 yds/lb. to 16,000 or 17,000 yds/lb. Typically,the fabric weighs 3 to 1012 ounces per square yard. Picks, i.e. fillingyarns per inch usually are from about 6 to about 120 or 140. Stitchlength is about 1-5 mm., preferably about 1 to 3 mm. lGauge runs fromabout 7 to 22 gauge, i.e. 7 to 22 stitches per inch across the fabric.Warp yarns may be the same as the number of stitch lines or less.

The polymeric foam may be of any of those known to the art provided thatthe foam must be applied as a fluid or must be capable of becoming afluid when on the fabric so that it can flow into the spaces betweenclusters of filling yarn. The polymer constituting the foam may berubber, polyurethane, polystyrene, vinyl polymers such as polyvinylchloride, polyethylene, phenolic resins, silicones and cellulose acetateor others. A very useful material is the cross-linked foamed copolymerof styrene and acrylic acid described in U.S. Pat. 3,215,647. This isformed from a latex containing a copolymer of styrene with anothermonomer having a reactive group such as acrylic acid. The latex alsocontains a coreactive material which cross-links the styrene polymer andwhich is soluble in water or water-miscible solvents. The latex isfoamed or frothed by bubbling in a gas or by decomposition of agas-releasing material. The latex is gelled and subsequently cured afterit has been applied to the above-described fabric.

The foam is applied to add a weight of about 0.50 to 10.0 ounces persquare yard and weighs about 10% to 100% of the fabric to which it isapplied. Ordinarily, the foam will be about 6 to 50 mils thick and havea density of about 3 to 16 pounds per cubic foot. These characteristicscontrol the flexibility of the foam and the lined fabric produced.Ordinarily, it is desired to reduce the flexibility of the fabricpartially, to improve its draping characteristics, but not to make itstilf. Therefore, flexible foam formulations are used.

The invention, briey described above, will be better understood from thefollowing description of a preferred embodiment, reference being made tothe drawing in which:

FIG. l is a plan View, partially in section, of the fabric of thisinvention, and

lFIG. 2 is a section along lines 2-2 of IFIG. 1.

The fabric illustrated in FIG. 1 comprises a plurality of loose iillingyarns 1 gathered into clusters 2. The clusters are held together bysewing thread 3 formed into interlocked chain stitching substantiallyperpendicular to the filling yarn clusters. Each sewing thread 3 isformed into a plurality of loops 4 spaced along the length of thefabric, each loop passing through the fabric at one of the spaces 5between. adjacent clusters 2.

The loops are formed into parallel chains, but each chain is formed fromtwo threads which alternately are formed into stitches of adjacentchains. For example, one chain of loops, designated 6 in the drawing, isformed from two threads 7 and 8. lA rst loop 9 is formed from thread 7,the next loop 10 is formed from thread 8 and the next loop 11 is formedfrom thread 7, etc. Thread 7 also is formed into loops 12 in chain 13 onone side of chain 6, alongside loop 10 and other loops in chain 6 whichare formed from. thread 8. Similarly, thread 8 also is formed into loops14 in a chain 1S on the other side of chain 6, alongside loops 9 and 11in chain 6. The arrangement is such that each sewing thread isinterlocked with two others in adjacent stitch lines so that, if athread breaks, it will not pull out a succession of stitches as it wouldif each chain were formed from a single thread.

FIG. 1 also illustrates warp yarns laid against the lling yarns and heldin place by the sewing threads as they extend back and forth betweenloop chains. Thus the interlocking chain stitch provides the furtheradvantage of making possible the use of warp yarn, which improvesdimensional stability of the fabric in the warp direction.

A foamed polymer material is applied to one side of the fabric describedabove. In a typical embodiment, a latex is applied which already hasbeen foamed. That is, the latex comprises polymer particles dispersed inwater, appropriate dispersing or emulsifying agents and small gasbubbles. The gas bubbles may have been generated by passing gas into thelatex with agitation to divide gas bubbles to suitable size.Alternatively, gas may have been generated by decomposing a chemicalagent, for example, an azo compound, which is dissolved or dispersed ina la-tex or a plastisol or organisol.

The foam or foamable material, once applied to the fabric in fluid form,seeps into the spaces 5 between clusters of filling yarn and encases thesewing thread passing through those spaces. The foam also surrounds thesewing thread on the side of the fabric which it covered and interlockswith the sewing thread. The effect is that the foam becomes an integralpart of the fabric, being firmly anchored lto the sewing thread. Thefoam also forms a layer 16 on one side of the fabric.

After the foam has flowed into the fabric, it is gelled and then cured.Gelling can be described as coagulating the very small polymer particlesinto larger masses which tend to flow together into a single continuouslayer containing dispersed gas. `Gelling may be obtained by heating.Curing may be described as the cross-linking of the polymer molecules,which increases their stiffness.

`Example 1 In a typical embodiment, the foam is the latex described inExample 1 of U.S. Pat. 3,215,647. This contains acopolymer derived from30 parts of styrene, 60 parts 1,3-butadiene and 10 parts acrylic acidand a crosslinking sys-tem comprising super Amide B-5, a coconut fattyacid diethanolamine condensate, and a water-solublemelamine-formaldehyde resin as well as suflicient water so that thesolids content is 42 percent. Small amounts of talc, titanium dioxideand zinc oxide were added as pigments and to reduce tackiness. The latexis mechanically foamed to a gas content of 75% by volume and flowed ontothe fabric. Then the fabric is placed in an oven which was maintained at350 'F., for 6- minutes which caused the latex yto gell and the polymerto cure. The foam had a density of about 8 pounds per cubic foot andformed a layer approximately 30 mil thick. The weight of foam was about3 ounces per square yard.

yAnother type of foam is derived from vinyl plastisol. An extensivediscussion of this type of foam is provided in Plastics EngineeringHandbook of The Society of the Plastics Industry, 3d Edition, (1960)especially at pages 18S-193. In a vinyl plastisol, the polymer usuallyis polyvinyl chloride in the form of small particles, which isintimately mixed with a plasticizer. The plastisols are quite Huid, but,on heating, they gel. It will be noted that gellation involves adifferent process in plastisols than in latex foam systems. In theplastisols, gellation is accomplished by heating which causes theplasticizer to diffuse into the polymer particles. The plasticizerinitially establishes a relatively high concentration at the surfaces ofthe particles, which makes them tacky so that they fuse together into acontinuous film. Further heating causes the plasticizer to diffusethroughout the film and form a smoothly integrated plasticized vinyl`lilm.

As in the case of latex foams, gas may be supplied by mechanicallydispersing a gas into the plastisol or by decomposition of a chemicalagent such as an azo compound. In the mechanical process, gas isintroduced into the chilled plastisol while it is under pressure. Thenthe plastisol and dissolved or dispersed gas is extruded through a tube.As the pressure is released, the gas expands to form interconnectingvoids. Then the plastisol is gelled by oven heating, e.g. at 360 F.

In the chemical foaming process, the plastisol is mixed with a chemicalagent which decomposes when heated. Various agents of this type areavailable, each having a characteristic decomposition temperature. Theagent for any particular system should have a decomposition temperaturebelow the gel temperature of the plastisol. The mixture is coated ontothe fabric and then heated in an oven. The chemical agent decomposes,causing foaming, and this is followed by gellation.

Similarly, iiexible polyurethane foam formulations may be used. Theseusually are obtained from a polyester or a polyether, a polyisocyanateand water and/ or a volatile inert liquid. Foaming is produced withcarbon dioxide generated by part of the polyisocyanate and Water or byevaporation of the volatile inert liquid.

Various coating techniques may be used to apply Huid foams. Theseinclude knife over roll, roller coating and casting. Since numeroussuitable polymer coating techniques already are well known, they neednot be described in detail here.

The foams normally contain pigments or dyes which render the fabricopaque and provide an ornamental effect. Opaqueness is provided by thecoordinated effects of the foam and the dye or pigment. The foam, havingnumerous air-polymer interfaces at different angles, scatters light eventhough the polymer itself may be transparent. Therefore little of anyincident light is transmit-ted. The light scattering also increases theeffectiveness of the dye or pigment. 'Ihat is, the scattered light has amuch longer path through the foam than it would have through a solidmass of polymer having the same thickness. Since the amount of lightabsorbed increases exponentially with the path length, the effectivenessof the pigments is greatly multiplied.

Almost any dye or pigment may be used which is compatible with thepolymer. If the dye or pigment has the same hue and depth of shade asthe coloring in the fabric, the product will appear to bc a tightlywoven-uniform color fabric. On the other hand, if a contrasting hue ordifferent depth of shade is used, an ornamental pattern will result.Consequently, the amount of dye or pigment used will vary with theeffect desired, but ordinarily it will be about to 75% by weight of thefoam. If chemical foaming agents are used, they preferably should beinert with respect to the dye or pigments used. It also is possible toprint on the exposed surface of the foam to produce other ornamentaleffects.

:In addition to the ornamental effects obtained with dyes or pigments,the laminated fabrics of the present invention have numerous otheradvantages. Compared to the loose filling chain stitched fabrics fromwhich they are derived, they have improved dimensional stability inlaundering and dry cleaning, improved tensile strength and tearstrength, improved sewing properties and seam strength, and importantimprovements in abrasion resistance. For example, fabrics of this type,Iwithout the foam lamination of the present invention, may shrink 6-8%in laundering, even if treated with crease proofing resins. However, inthe fabrics of the present invention, shrinkage is -within normallimits. As noted above, the fabrics have improved draping properties.They also have better insulating properties, especially if the foam isof the closed pore type.

In part, these properties result from the inherent nature of the fabric.IIn open mesh fabrics, there is a tendency for the iiuid foam materialto flow through openings from one side of the fabric onto the otherside. 'Ihs is obser-ved in open Casement type fabrics. However, becauseof the nature of the fabric used in the present invention, cornposed ofloose filling, sewing, and optionally -warp threads, excessive migrationof the foam to the exposed face of the fabric is avoided.

The following examples further illustrate the invention.

lExample 2 parts cross-linking resin; 4.2 parts frothing soap; 0.3

part polyacrylate thickener; 7.2 parts zinc oxide; 50 parts aluminumhydrate filler'and .25 part methyl cellulose.

The compound was mechanically foamed and suicient air injected to give adry foam weight of approximately ten pounds per cubic foot. The foam wasapplied at a thickness to give an add-on of 1.50 to 2.0 oz./yd.2 offoam. After application, foam was dried and cured for a total of fiveminutes at 300 F. The laminate was washed and dried to evaluatestabilization. The warp direction showed .25% shrinkage compared to 8.9%for uncoated control. The filling direction showed 0% shrinkage comparedto 4.2% for control.

Example 3 The fabric described in Example l 'was coated with a latexfoam compound based on a copolymer similar to that described in Examplel of U.S. Pat. 3,215,647. This particular latex contains thecross-linking resin and frothing soap and is identified as Dow LatexQW-397l. The foam compound consisted of parts latex; 40 parts talcfiller; 20 parts titanium dioxide; l part zinc oxide; l part methylcellulose and sufficient water to give a compound viscosity of 5,600cps.

The compound was mechanically foamed to give a density of l5 pounds percubic foot. A thickness of 15 mils was applied and gave a dry foamadd-on of 2.6 to 3.2 oz./yd.2. The laminate Iwas dried under infraredlamps and further cured in an oven at 310 F. for 31/2 minutes. Thelaminate showed excellent opacity and physical properties exceeded thoseof the untreated control.

{Example 4 A drapery fabric similar to that described in Example l wascoated with an open cell mechanically blown polyvinyl chloride foam. Theplastisol for the foam consisted of 100 parts plastisol grade PVC resin;95 parts octydecyl phthalate; 5 parts epoxy plasticizer; 3 partsbarium-cadmium-zinc stabilizer; 15.4 parts titanium dioxide, 12 partssilicone surfactant such as Dow Corning DC-XR-6-370l. The plastisolviscosity was 3,000 cps.

The plastisol was fed into a mechanical foamer and air flow adjusted togive a foam density of 16-18 pounds per cubic foot. Foam was applied atlevels of 5 to 35 mils in thickness. Drying and curing were accomplishedby heating for six minutes in a forced :air oven set at 325 F.

The fabrics coated fwith this foam showed excellent stability to washingand a ivery noticeable improvement in abrasion resistance.

The product may receive various finishing treatments for waterrepellency, softening, reduced soiling, improved soil release duringlaundering, crease-proofing and the like, including the resin treatmentdescribed in U.S. patent application of Jones et al., Ser. No. 651,478,filed July 6, 1967. The foam can be embossed for other ornamentaleffects. Various other changes may be made in details of constructionand mode of operation Iwithout departing from the scope of theinvention, as defined in the appended claims.

We claim:

1. A laminated fabric comprising a first layer comprising a plurality ofloose filling yarns substantially gathered in clusters separated byspaces and a plurality of loop chains of sewing thread extending alongone surface of said layer generally perpendicular to said loose fillingyarn with stitches through said spaces and sewing thread connectingbetween said loops extending through said spaces and along the othersurface of said layer,

and, as a second layer a foamed polymer closely conforming to onesurface of said first layer and to said loose filling yarns on thatsurface of said first layer and intimately surrounding said sewingthread on said one side and in said spaces, and extending at leastpartly through said spaces, so as to cover one of the surfaces of saidfirst layer, the other surface of said first layer being exposed,

so that said foam is substantially integral with said first layer and isinterlocked with the yarn and sewing thread thereof.

2. A laminated fabric as set forth in claim 1 in which there are about6-140 of said loose filling yarns per inch of fabric length and saidspaces through which said sewing thread stitches pass are about lmm.apart.

3. A laminated fabric as set forth in claim 2 in which said first layerhas a weight of about 3 to 12 ounces per square yard and said secondlayer has a Weight of about 0.5 to 10.0 ounces per square yard.

4. A laminated fabric as set forth in claim 3 in which said second layerweighs about -100% of the weight of said first layer.

5. A laminated fabric as set forth in claim 4 in which said second layeris about 6 to 5() mils thick and has a density of 3 to 16 pounds percubic foot.

:3. A laminated fabric comprising:

a first layer comprising a plurality of loose filling yarnssubstantially gathered in clusters separated by spaces, said yarns beingabout 3,000-20,000 yards per pound and about 6 to 140 picks per inchalong said fabric, and a plurality of loop chains of sewing threadextending along one surface of said first layer generally perpendicularto said loose filling yarn with stitches through said spaces and sewingthread connecting between said loops extending through said spaces andalong the other surface of said layer, said sewing thread being about 40to 200 denier, the sewing thread stitches being about l to 5 mm. longand about 7 to 22 per centimeter across the fabric, substantially eachsewing t read end being alternately formed into loops in a pair ofadjacent loop chains and substantially each of said loop chains havingalternate loops of two different sewing thread ends, said first layerhaving a weight of about 3-12 ounces per square yard, and, as a secondlayer, a-foamed polymer closely conforming to one surface of said firstlayer and to said loose filling yarns on that surface of said firstlayer and intimately surrounding said sewing thread on said one side andin said spaces, and extending at least partly through said spaces, so asto cover one of the surfaces of said first layer, the other surface ofsaid first layer being exposed, said second layer having a weight ofabout 0.50 to 10.0 ounces per square yard, a density of about 3 to 16pounds per square foot, a thickness of about 6 to 50 mils, and a weightabout 10-100% of the weight of said rst layer,

said foam being substantially integral with said first layer.

References Cited UNITED STATES PATENTS 3,274,806 9/1966 Duhl 66-1923,058,194 10/1962 Havner 16k-89X 2,410,748 11/1968 Blue ll-89X 3,381,5025/'1968 Turton 66-192 JOHN T. GooLKAsrAN, Primary Examiner J. C. GIL,Assistant Examiner

